combine_json.sh

#!/bin/bash

#Help to display if the args are wrong
usage() { echo "Usage: $0 -o path/to/output.json" 1>&2; exit 1; }

#Show help if the args are wrong
while getopts ":o:" ARG; do
    case "${ARG}" in
        o)
            OUTPUT_FILE=${OPTARG}
            ;;
        *)
            usage
            ;;
    esac
done
shift $((OPTIND-1))

#Show help if the -o arg is missing
if [ -z "${OUTPUT_FILE}" ]; then
    usage
fi

#Function to get an absolute path from a relative path
function realpath { echo $(cd $(dirname $1); pwd)/$(basename $1); }
REAL_OUTPUT_PATH=$(realpath $OUTPUT_FILE)

#Begin writing combined JSON
echo "{" > $OUTPUT_FILE

FILES_ADDED=0
#Loop all JSON files in the current dir (including within nested dirs)
find . -type f -name '*.json' | while read FILENAME; do
  #Get the contents of the file
  JSON=$(cat $FILENAME)
  #Trim the opening and closing braces and any surrounding whitespace
  TRIMMED="$(echo $JSON | sed -e 's/^[[:space:]]*{[[:space:]]*//' -e 's/[[:space:]]*}[[:space:]]*$//')"

  #If we're not reading the output file and the contents is not empty
  if [[ $(realpath $FILENAME) != $REAL_OUTPUT_PATH ]] && [[ ! -z $TRIMMED ]]; then
    echo "Appending $FILENAME"
    #Comma separate consecutive file contents
    [[ $FILES_ADDED != 0 ]] && echo -n ', ' >> $OUTPUT_FILE
    echo -n "$TRIMMED" >> $OUTPUT_FILE
    ((FILES_ADDED++))
  fi
done

#Finish writing combiend JSON
echo "}" >> $OUTPUT_FILE

#Prettify the output JSON
OUTPUT=$(python -m json.tool $OUTPUT_FILE)
echo "$OUTPUT" > $OUTPUT_FILE

echo "JSON written to $OUTPUT_FILE"